1. Field of the Invention
This invention relates to a lens apparatus, a camera system and a camera, and particularly is suitable for an optical apparatus such as, for example, a video camera or a still camera using two drive mechanisms, i.e., a first drive mechanism and a second drive mechanism, as a drive source for driving a focusing lens in the direction of the optical axis thereof, and designed such that the two drive mechanisms are driven independently of each other, whereby high-speed and highly accurate drive control can be effected.
2. Related Background Art
There have heretofore been proposed numerous optical apparatuses (camera systems) carrying thereon an automatic focus adjusting (hereinafter referred to also as “AF”) apparatus for detecting the focus adjusted state of a photo-taking lens or the distance to an object, and driving an actuator (drive source) such as a motor on the basis of the result of the detection to thereby drive a focusing lens to an in-focus position.
With the downsizing and high-density pixel integration of digital camera systems in recent years, numerous propositions regarding the higher accuracy of the AF apparatus and the shortening of the AF time have been made (for example, Japanese Patent No. 2687292 and Japanese Patent Application Laid-Open No. H09-181954).
Japanese Patent No. 2687292 discloses an AF apparatus having focus rough adjusting means for adjusting a focusing system lens to thereby effect the rough adjustment of the focus, and wobbling method detecting means for finely vibrating the lens and adjusting the focus thereof by a wobbling method.
Japanese Patent Application Laid-Open No.. H09-181954 discloses a focus controlling method using two means, i.e., focus controlling means by a phase difference detecting process and focus controlling means by a contrast detecting process, and selecting one or two of these means in due order to thereby effect focusing.
The AF apparatus of Japanese Patent No. 2687292 is such that different ones of a plurality of focusing system lenses are driven by different actuators, but for rough adjustment, a first focusing system lens is manually driven, and a second focusing system lens is vibrated by the wobbling method, and the first focusing system lens is driven so as to assume the best focus position.
In the conventional AF apparatus as described above, however, rough adjustment must be manually effected and there is a limitation in the driving accuracy of the focusing system lenses, and there has been the problem that hunting occurs.
The focus controlling method of Japanese Patent Application Laid-Open No. H09-181954 has AF mode changeover means for changing over a one-shot AF mode using both of the focus controlling means by the phase difference detecting process and the focus controlling means by the contrast detecting process in due order, and a servo AF mode using the focus controlling means by the phase difference detecting process.
However, two kinds of controlling methods are used as the focus controlling methods in Japanese Patent Application Laid-Open No. H09-181954, but the focusing lens is single and the actuator (drive source) therefor is also single, and there has been the tendency-that highly accurate AF must be performed within a short time by only these controlling methods.
When as a method of solving this, for example, a high-speed type actuator is used to shorten the focusing time, it is possible to shorten the time for which the focusing lens is driven to the vicinity of the in-focus position, but there has been the tendency that the control during minute driving from the vicinity of the final in-focus position to the in-focus position is not in time and it becomes difficult to accurately stop the focusing lens at the in-focus position.
Also, when conversely, a low-speed type actuator is used with priority given to higher accuracy, it is possible to accurately stop the focusing lens during the minute driving from the vicinity of the in-focus position to the in-focus position, but the driving time to the vicinity of the in-focus position has tended to become long.